In eye tracking applications, digital images are retrieved of the eyes of a user and the digital images are analyzed in order to estimate the gaze direction of the user. There are different methods for achieving such an estimation. In some methods ambient light is used when retrieving images of the eyes of the user and in some methods additional light sources (illuminators) are used to illuminate the eyes for retrieving images of the eyes of the user. Generally, the estimation of the gaze is based on identification of the pupils of the eyes of the user, together with identification of glints (corneal reflections) in the eyes of the user. In order to identify a pupil of an eye in an image of the eye, the contrast between a representation of the pupil and a representation of an iris of the eye in the image must be sufficient.
One known method of eye tracking includes the use of infrared light and an image sensor. The infrared light is directed towards the pupil of a user and the reflection of the light is captured by an image sensor. Through analysis of the reflection point, the direction of the user's gaze may be calculated. One such system is described in U.S. Pat. No. 7,572,008 (which is hereby incorporated by reference in its entirety).
Portable or wearable eye tracking devices have also been previously described. One such eye tracking system is described in U.S. Pat. No. 9,041,787 (which is hereby incorporated by reference in its entirety). A wearable eye tracking device is described using illuminators and image sensors for determining gaze direction.
In applications of eye tracking for in portable or wearable eye tracking devices, such as in virtual reality (VR) devices, where head mounted devices are used which include an eye tracking system determining an eye direction and/or gaze direction based on a pupil center and glints from illuminators illuminating a user's eyes, problems can arise for example for a user who is wearing a pair of spectacles under the VR glasses. For example, one or more reflections from an optic arrangement of the pair of spectacles caused by the one or more of the illuminators may result in a situation where the pupil cannot be accurately identified or where no or too few glints can be identified for eye tracking. In such situations it will be difficult or impossible to determine eye direction and/or gaze direction and or eye direction or at least not with desirable reliability.
It would be desirable to provide an eye tracking technology to account for such situations where reflections from glasses worn under VR glasses reduce the accuracy of eye tracking or makes it difficult or impossible to determine eye direction and/or gaze direction for eye tracking.